An electrostatic model for collagen fibrils. The interaction of reconstituted collagen with Ca++, Na+, and Cl−

作者：Shu‐Tung Li, Elton P. Katz · 发表于：Biopolymers · 年份：1976 · DOI：10.1002/bip.1976.360150802 · 被引用次数：71 · 研究领域：Collagen: Extraction and Characterization、Mass Spectrometry Techniques and Applications、Calcium Carbonate Crystallization and Inhibition

Abstract A model for the electrostatic properties of hydrated collagen fibrils, based on the concept of a “penetrable” protein, has been evaluated through studies of collagen fibrils that had been chemically modified to change their electrostatic properties,. A value of 0.28 ± 0.07 ml/g was found for the intrafibrillar space sterically inaccessible to a molecule that had an equivalent spherical radius of 4.5 Å. The net intrinsic charge on reconstituted collagen is +14 mol/mol under physiological conditions, but decreases, at constant pH, with ionic strength. A value of 7.1 for the pK of the histidine and α‐amino groups in reconstituted collagen was obtained through the application of the electrostatic model to this effect. The values obtained for calcium binding parameters for collagen fibrils, under solution conditions in which the nonspecific electrostatic properties of collagen fibrils were eliminated (3–5 M tetramethyl ammonium chloride), were in agreement with values obtained in 0.16 M NaCl solutions calculated through the use of the electrostatic theory. These are 0.73 ± 0.23 and 56.2 ± 12.3 sites per molecule with intrinsic association constants of 1101 ± 386 and 21.4 ± 5.2 M−1, respectively. The model also predicts that an average 4‐mV potential difference exists between the reconstituted collagen fibrils and physiological solutions, and that collagen fibrils under such conditions have piezoelectriclike properties. The pattern of interaction of ions with collagen fibr...